Conventionally, a known printed wiring board includes a thin plate metal reinforcing member formed by performing nickel plating on a surface of a stainless steel plate at an mounted position for an electronic component (PATENT LITERATURE 1). Accordingly, nickel functions as a protecting layer against heat and humidity in the stainless steel plate in the printed wiring board. This allows for reinforcing the mounted position for the electronic component with the metal reinforcing member while maintaining a ground effect.